The present invention relates to a varnish coating apparatus for coating a sheet-like matter with varnish to prevent stains on a printed sheet-like matter or obtain a better appearance of it and, more particularly, to a varnish coating apparatus for coating both surfaces of a sheet-like matter with varnish in a single path.
Japanese Patent Laid-Open No. 10-296953 (reference 1) discloses a coating apparatus which coats both surfaces (obverse and reverse surfaces) of a sheet-like matter with varnish in a single path without inverting the sheet-like matter. A coating unit 80 disclosed in reference 1 is arranged downstream in the paper convey direction of a printing section (not shown). The coating unit 80 has a blanket impression cylinder 82 in contact with a transfer cylinder 81 of the printing section, and first and second varnish coating units 83 and 84, as shown in FIG. 8.
The first varnish coating unit 83 is arranged upstream in the paper convey direction from the contact point between the blanket impression cylinder 82 and the transfer cylinder 81. The first varnish coating unit 83 is constituted by a varnish pan 86a which stores varnish, a fountain roller 87a dipped in varnish in the varnish pan 86a, a metering roller 88a in contact with the fountain roller 87a, a form roller 89a in contact with the metering roller 88a, and a coater cylinder 85a in contact with the form roller 89a and opposing a paper sheet held by the transfer cylinder 81.
In this arrangement, varnish in the varnish pan 86a is transferred to the coater cylinder 85a through the fountain roller 87a, metering roller 88a, and form roller 89a and then to the peripheral surface of the blanket impression cylinder 82 through the coater cylinder 85a. The first varnish coating unit 83 which is arranged upstream in the paper convey direction from the contact point between the blanket impression cylinder 82 and the transfer cylinder 81 transfers varnish to the peripheral surface of the blanket cylinder 82 before it receives the paper sheet from the transfer cylinder 81. Accordingly, when the paper sheet transferred from the transfer cylinder 81 to the blanket impression cylinder 82 passes through the contact point between the blanket impression cylinder 82 and a coater cylinder 85b of the second varnish coating unit 84, varnish transferred to the peripheral surface of the blanket impression cylinder 82 is transferred to the reverse surface of the paper sheet by the printing pressure of the coater cylinder 85b so that the reverse surface is coated with varnish.
The second varnish coating unit 84 is arranged downstream in the paper convey direction from the contact point between the blanket impression cylinder 82 and the transfer cylinder 81. Like the above-described first varnish coating unit 83, the second varnish coating unit 84 is constituted by a varnish pan 86b, a fountain roller 87b, a metering roller 88b, a form roller 89b, and the coater cylinder 85b. In this arrangement, varnish in the varnish pan 86b is transferred to the coater cylinder 85b through the fountain roller 87b, metering roller 88b, and form roller 89b. When the paper sheet passes through the contact point between the blanket impression cylinder 82 and the coater cylinder 85b, varnish on the coater cylinder 85b is transferred to the obverse surface of the paper sheet so that the obverse surface is coated with varnish.
After coating, the paper sheet is gripped from the transfer cylinder 81 by the blanket impression cylinder 82. The paper sheet whose obverse and reverse surfaces are coated with varnish is gripped by delivery grippers (not shown) of a delivery chain 91. The gripped paper sheet is conveyed by the delivery chain 91. The applied varnish is dried by drying units 92, 93, and 94 during conveyance. Then, the paper sheet is dropped onto a delivery pile (not shown) and stacked.
In the conventional coating apparatus, when pattern coating or partial coating is necessary for the obverse surface of a paper sheet, a printing plate having a projecting portion is attached in correspondence with a patterned coating portion in place of the blanket attached on the peripheral surface of the coater cylinder 85b of the second varnish coating unit 84.
However, as shown in FIG. 9, if double-side coating is to be performed in which a pattern coating region 9B on the reverse surface of a paper sheet 9 does not overlap a pattern coating region 9A of the obverse surface of the paper sheet 9, the pattern coating region 9B on the reverse surface is pressed by the recessed portion of the printing plate, and therefore, no sufficient printing pressure is applied to the coating region 9B on the reverse surface. In addition, when full coating is to be performed on the reverse surface, no sufficient printing pressure is applied to the reverse surface region that does not correspond to the pattern coating region on the obverse surface. For this reason, the conventional coating apparatus cannot perform pattern coating on the reverse surface of a paper sheet when the obverse surface of the paper sheet is to be pattern-coated.
To solve this problem, a coating apparatus disclosed in Japanese Patent Laid-Open No. 2000-103035 (reference 2) is proposed. The coating apparatus disclosed in reference 2 has a first coating unit which coats the obverse surface of a paper sheet on the peripheral surface of an odd-numbered cylinder (to be referred to as an odd-number cylinder hereinafter) located from the upstream side to the downstream side in the paper convey direction, a second coating unit which coats the reverse surface of the paper sheet on the peripheral surface of an even-numbered cylinder (to be referred to as an even-number cylinder hereinafter), and a drying unit arranged downstream of each coating unit.
In this arrangement, the obverse surface of a paper sheet is coated by the first coating unit on the peripheral surface of an odd-number cylinder. After that, the varnish applied to the obverse surface is dried by the drying unit. Subsequently, the reverse surface of the paper sheet is coated by the second coating unit on the peripheral surface of an even-number cylinder. After that, the varnish applied to the reverse surface is dried by the drying unit. In this way, the obverse and reverse surfaces of a paper sheet are coated selectively on the odd-and even-number cylinders, thereby making pattern coating on both the obverse and reverse surfaces of a paper sheet.
In the above-described coating apparatus, however, since the obverse and reverse surfaces of a paper sheet are selectively coated on the odd- and even-number cylinders, a cylinder dedicated to obverse surface coating and that dedicated to reverse surface coating are necessary. This increases the manufacturing cost and also increase the total length of the machine. In addition, in winding a paper sheet around the cylinder dedicated to reverse surface coating after obverse surface coating, a drying unit is required to prevent varnish on the obverse surface of a paper sheet from sticking to the cylinder dedicated to reverse surface coating. In this case, the varnish must be dried in a short time. To do this, a bulky drying unit is necessary, resulting in an increase in manufacturing cost.
It is an object of the present invention to provide a coating apparatus capable of reliably executing double-side coating including pattern coating on the reverse surface of a sheet-like matter.
It is another object of the present invention to provide a varnish coating apparatus which reduces the size and manufacturing cost.
In order to achieve the above objects, according to the present invention, there is provided a varnish coating apparatus comprising a first varnish film forming cylinder having a first supply surface to which varnish is supplied, a second varnish film forming cylinder having a second supply surface to which varnish is supplied, a first blanket cylinder having a first transfer surface in contact with the first supply surface of the first varnish film forming cylinder and a first opposing surface corresponding to the second supply surface of the second varnish film forming cylinder, and a second blanket cylinder arranged in contact with the first blanket cylinder and having a second transfer surface in contact with the second supply surface of the second varnish film forming cylinder and a second opposing surface corresponding to the first supply surface of the first varnish film forming cylinder, wherein when a sheet passes through a contact point between the first and second blanket cylinders, the first transfer surface of the first blanket cylinder opposes the second opposing surface of the second blanket cylinder to perform varnish coating on a first surface of the sheet, and the second transfer surface of the second blanket cylinder opposes the first opposing surface of the first blanket cylinder to perform varnish coating on a second surface of the sheet.